font-family: "Trebuchet MS", Arial, Helvetica, sans-serif;
Another advantage of using cascading style sheets (CSS) is you have total control over the div tags that make up your page. Amending the CSS code will automatically update multiple pages within your website that are using the specific ID or Class you have altered.
Unless of course the selector and associated attributes are locked as part of the template, if you do plan on locking a particular part of your page to the template like your header, navigation and footer there is no need to make them class selectors as they will be locked to the template. It is really the selectors that appear within editable regions you have created we need to focus on; if you plan on calling upon the attributes to use on multiple pages then you should apply the class selector.